1. Field of the Invention
The present invention relates to a voltage non-linear resistor consisting essentially of zinc oxide.
2. Related Art Statement
Heretofore, resistors consisting essentially of zinc oxide and containing a small amount of an additive, such as Bi.sub.2 O.sub.3, Sb.sub.2 O.sub.3, SiO.sub.2, Co.sub.2 O.sub.3, or MnO.sub.2 , etc., have been widely known as superior voltage non-linear resistors, and have been used as arrestors or the like using such characteristic property.
Among such additives, bismuth oxide has .alpha., .beta., .gamma. and .delta. type crystal phase, but a bismuth oxide in conventional zinc oxide element is usually only .beta. phase, .gamma. phase or .beta.+.gamma. phase.
Crystal phases of bismuth oxide in the zinc oxide element have large influences on characteristics of the varistor, so that optimum crystal phases have to be used. If .beta. phase is only used, the life performance against applied voltage becomes short and discharge current withstanding capability is decreased. While, if .gamma. phase is only used, current leakage becomes large, the index .alpha. of voltage non-lineality becomes small, and electrical insulation resistance also becomes low. If .beta.+.gamma. phase is only adopted, a mutual ratio of .beta. and .gamma. relative to each other is unstable and constant characteristic properties can not be obtained.